There's so many! Off the top of my head: in front of Grauman's Chinese Theater (houses GMR), the terrace at TOT, the brushy area around Star Tours, random spots on Hollywood Blvd, over by the Brown Derby, in front of either the Muppet Fountain or the fountain by the Tips & Times board.
Also, I think it depends what type of look you're going for in your pics. If you're looking for more 'posed' type shots, you may be better off at Epcot.